The invention relates generally to the dissolution and dilution of concentrated solid materials and more specifically to the controlled dissolution and dilution of concentrated solid warewashing detergents to form concentrated liquid solutions. Detergent concentration control is provided exclusively via hydraulic means with no electronic detection of water usage or level, electronic control of detergent content or usage or electronic control of mechanical components.
A number of different techniques have been developed and used for converting solid chemicals used in cleaning processes into a aqueous concentrated solution. For example, devices designed for a powdered, flaked or granular detergent are disclosed in Daley et al, U.S. Pat. No. 3,595,438, issued Jul. 27, 1991; Moffet et al, U.S. Pat. No. 4,020,865, issued May 3, 1977; and Larson et al, U.S. Pat. No. 4,063,663, issued Dec. 20, 1977. Another form of solid detergent is the pre-shaped detergent briquette. Dispensing systems for dissolving detergent briquettes are known in the art. See, for example, U.S. Pat. Nos. 2,382,163; 2,382,164; and 2,382,165 all issued Aug. 14, 1945 to MacMahon; and U.S. Pat. No. 2,412,819, issued Dec. 17, 1946 to MacMahon.
One recent form of solid detergent is the solid block form. The detergent block may comprise a detergent extruded or cast within a mold or container or as a detergent block which is free-standing. Dispensing systems for these solids are known in the art. See, for example, U.S. Pat. No. 4,426,362, issued to Copeland et al and commonly owned U.S. Pat. Nos. 4,569,781 and 4,569,780, issued Feb. 11, 1986, to Fernholz et al. The cast detergent is dispensed by spraying a solvent onto the detergent block within the container, thereby dissolving the exposed surface of the detergent to form a concentrated working solution. The concentrated working solution falls into a reservoir or is directed by a conduit to the wash tank of a washing apparatus. When the chemical compound within the container is completely utilized, the exhausted container may be simply discarded and a fully charged container may be placed in the dispenser.
Solid, cast chemicals used in cleaning processes are preferably cast in a sturdy container which can act as a mold, a shipping and storage container, and a dispenser housing. The cast chemical may be dispensed by inverting the container over a spray nozzle and impinging solvent directly onto the exposed surface or surfaces of the chemical contained therein. The container may either be retained within the dispenser as the chemical is being used, or the chemical may be removed from the container and placed into the dispenser. However, hazardous chemicals used in cleaning processes such as highly alkaline detergents are preferably packaged such that they can be dispensed without coming into physical contact with the human body.
Known dispensing devices have sought to maintain a relatively constant rate of the chemical being dispensed, or a constant concentration, by maintaining a fixed distance between the dissolving spray nozzle and the exposed and erodible surface of the solid block of chemical. See, for example, commonly owned U.S. Pat. No. 4,687,121, issued to Copeland on Aug. 18, 1987; U.S. Pat. No. 4,690,305, issued to Copeland on Sep. 1, 1987, and U.S. Pat. No. 4,826,661, issued to Copeland et al May 2, 1988. Alternatively, a separate control system has regulated the amount of detergent dispensed and has maintained a constant concentration, thereby making it unnecessary to control the nozzle to-eroding surface distance.
In many situations, however, it is desirable for the chemical concentration to be variable. The optimum chemical concentration depends upon such factors as the type of solid chemical being dispensed, the type of surface being cleaned, the amount of soil being removed from the fabric or surface being cleaned, the temperature of the solvent, the degree of mechanical action applied to the fabric or surface being cleaned, and the volume of cleaning solution being produced. In the past, adjusting the concentration of the cleaning solution has typically been done manually by the operator. That is, a certain amount of cleaning solution has been dispensed from the solid chemical, to which a certain amount of water is added. If a higher use solution concentration is desired, then less water is added to the concentrated cleaning solution. However, this procedure does not result in a consistent, precise, and controlled solution concentration, and often results in the use solution having either too much or too little cleaning chemical concentration.
U.S. Pat. No. 2,371,720 to Stine discloses an admixing and dispensing device applied to dishwashing machines. One of the objects of the invention is to xe2x80x9cprovide a method and device in which the rate of admixture is governed and controlled automatically by the flow of liquidxe2x80x9d. An upwardly disposed spray nozzle 10 projects a spray of water against a conical screen 8. The conical screen 8 supports a mass of caked or powdered chemical detergent. The water to the nozzle is provided by a pipe 20 which is the main rinse water supply. Water is directed to spray nozzle 10 through valve 15 and pipe 11. Valve 15 is of a design such that it also transmits a flow, proportional to the flow, through to a rinse line.
U.S. Pat. No. 2,308,612 to Lehmkuhl discloses a dissolving apparatus in which water from a spray head 61 falls upon powdered detergent. The detergent is held in an inner container 31 which has a foraminous partition 41 in its center. The concentration of the dissolved powder in the liquid is adjusted by moving the nozzle closer to or further from the detergent powder. Adjusting the height of the nozzle changes the relative proportions of the water sprayed into the inner container holding the detergent and water sprayed into the space between the side walls of the inner and outer containers.
U.S. Pat. No. 3,727,889 to Nagel discloses a fluid conduit 38 provided with a nozzle which projects a jet of liquid against a dry chemical. An automatically controlled valve 44 dispenses a predetermined amount of liquid against the chemical. The disclosure describes the control means 46 by a block diagram labeled xe2x80x9ccontrolxe2x80x9d and states that xe2x80x9csuitable automatic control means [are] well known in the artxe2x80x9d. The specification discloses a selector dial to select the amount of dilution water for a given cycle.
U.S. Pat. No. 4,964,185 to Lehn discloses a pressure regulating valve 35 which maintains a constant flow rate of solvent to spray nozzle 31. The spray nozzle sprays the solvent onto solid or granular chemicals retainably held above the nozzle. The device forms a concentrated chemical solution and controls the amount of chemical dispensed.
U.S. Pat. No. 5,505,915 to Copeland et al. discloses a solid chemical dispenser in which distance between the nozzle and the detergent can be varied. The position of the nozzle can be varied by a mechanical linkage or an automatic means such as a servo system.
U.S. Pat. No. 3,982,666 to Kleimola ct al. discloses a means to sequentially and automatically inject various liquid products into a laundry washing machine. The invention utilizes a signal generating device for generating electrical signals of a predetermined duration.
U.S. Pat. No. Reissue 32,818 to Fernholz et al. discloses a method of using a cast detergent-containing article. The patent describes positioning the solid detergent over xe2x80x9cspray means which is connected to a water sourcexe2x80x9d.
There remains a need for a simple, accurate method of dissolving and diluting a concentrated solid warewashing detergent using solely hydraulic control without complicated electronic control of water, chemical or mixing.
Accordingly, the invention involves a hydraulic method for dispensing and controlling detergent and rinse aid use and active concentration in a warewashing machine. Accurate dispensing and control of active detergent concentrations is obtained with no electronic detection or control of concentration. The value of the invention is that it uses fully hydraulic methods and avoids the complexity inherent in the use of electronic or electric controls. The dispensing means can have electronic components in the rinse feed system, with no electronic control of the detergent feed. The warewashing machine is plumbed such that a portion of the service water from a water supply such as the final rinse line is diverted to a water, spray-on solid block detergent dispenser. The volume of water impinging on the solid detergent that governs the amount of detergent dispensed is in turn governed by volume-limiting or flow-limiting metering tips. A metering tip is selected with the time elapse or time period extent of the rinse cycle in mind such that the amount of time water flows in the rinse step dispenses (using the bypassed water) the correct amount of detergent by the spray-on function. Whenever the rinse line is operated, in a periodic manner at in repeated time period and at a constant pressure, the correct amount of detergent is dispensed solid detergent is dispensed to maintain the effective correct cleaning amount of detergent in the wash water. With the appropriate size of metering tip in the dispenser and the correct timing of the final rinse cycle, the appropriate proportions of aqueous detergent and rinse volume can be obtained in the machine to achieve both effective cleaning and rinsing. The machine can be economically operated by appropriate settings of rinse volume, rinse timing and a metering tip for the water impinging on the solid detergent in the dispenser. Once the metering tips are calibrated for an installation the machine will typically dispense consistently until the local service water pressure changes substantially.
The invention is found in an apparatus for maintaining an effective concentration of alkaline detergent in an aqueous wash or aqueous medium in a warewashing machine, which apparatus comprises a batch-fill warewashing machine having an aqueous rinse system, an alkaline detergent dispenser and a sump sized for a predetermined volume of the alkaline detergent in the aqueous medium; a source of the aqueous medium fluidly connected to the rinse system; means for controlling the flow of the aqueous medium through the rinse system; diverting means for obtaining a predetermined portion of the aqueous flow from the rinse system and for directing the diverted portion through a metering cap and volume control to the alkaline detergent dispenser, thereby to dissolve the alkaline detergent; and means for directing the dissolved alkaline detergent to the sump; wherein the detergent is dispensed only in a rinse cycle and an effective concentration of alkaline detergent is maintained in the warewashing machine sump.